Multicoloured tips of iron, Roman in origin (10)

I believe the answer is:

iridescent

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'multicoloured' is the definition.
Both the answer and definition are adjectives. Maybe there's an association between them I don't understand?

'tips of iron roman in origin' is the wordplay.
'tips of' suggests taking the first letters (I've seen 'tip of' mean this).
'origin' becomes 'descent' (synonyms).
The initial letters of 'iron roman in' is 'iri'.
'iri'+'descent'='IRIDESCENT'

Can you help me to learn more?

(Other definitions for iridescent that I've seen before include "with a glittering display" , "flashing colours" , "changing colour" , "Showing luminous colours" , "shimmering with colour" .)

I've seen this clue in The Independent.

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